Difference of 4 Wire Resistance Measurement Result Depending on the Switch

Updated May 24, 2019

Reported In

Hardware

  • PXI-4071
  • PXI-407X
  • PXIe-4081
  • PXIe-4082
  • PXIe-4080
  • PXI-4070
  • PXI-4072

Issue Details

I am using PXIe-4081 with PXIe-2530B to measure one resistor several times. When I measured several times using the switch module, the result is that the resistance value drops gradually. Why do I get this problem? How I resolve the problem?

Solution

NI Digital Multimeters (DMMs) has an offset compensated ohms function. it applies to both 2 -wire and 4-wire resistance. If you use switching system using uncompensated read relays can have offset voltage > 10µV due to the Kovar lead material used at the device glass seal. To solve the problem that the resistance value drops, you can use niDMM Configure Offset Comp Ohms(VI). You should set Offset Compensated Ohms control input as ON.

Additional Information

Offset Compensated Ohms is a Digital Multimeter feature provided for eliminating offset voltages in a resistance (ohms) test system. Whether 2-wire or 4-wire, Offset Compensated Ohms applies and the concept is the same. You have learned about the challenges of removing offset resistances (ohms) from the measurement, however, Offset Compensated Ohms is different—it acts on offset voltages. You can understand about resistance measurement using Resistance Measurements Tutorials.

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